System and method for configuring an IP telephony device

ABSTRACT

System and method for IP telephony. The system includes an IP telephone (IPT) and a Service Gateway (SG). The SG receives an identifier, e.g., a vendor class identifier, included in a DHCP discover message from the IP telephone and determines if the identifier is valid. If so, the SG issues a DHCP offer comprising DHCP lease information to the IP telephone, including a range of port numbers assigned to the IP telephone based on the identifier, where the range of port numbers comprises ports which are not reserved for use by other IP protocols. The DHCP lease information includes information indicating operational software for the IP telephone which the IP telephone executes to enable IP communications. The SG mediates IP communications between the IP telephone and an IP device, where the IP telephone uses at least a subset of the range of port numbers to send or receive IP communications.

PRIORITY CLAIM

This application claims benefit of priority of U.S. provisionalapplication Ser. No. 60/281,908 titled “SYSTEM AND METHOD FOR IPTELEPHONY” filed Apr. 3, 2001, whose inventors were Richard E. Fangmanand Jason D. Preston.

FIELD OF THE INVENTION

The present invention relates to the field of telephony, and moreparticularly to Internet Protocol (IP) based telephony.

DESCRIPTION OF THE RELATED ART

Voice over Internet Protocol (VOIP) refers to the technology to maketelephone calls and send faxes over IP-based data networks with asuitable quality of service (QoS) and superior cost/benefit. The mainjustifications for development of VoIP can be summarized as follows:

Cost reduction—VoIP technologies can provide substantial savings in longdistance telephone costs, which is extremely important to mostcompanies, particularly those with international markets.

Simplification—An integrated voice/data network allows morestandardization and reduces total equipment needs.

Consolidation—The ability to eliminate points of failure, consolidateaccounting systems and combine operations, providing for more efficientoperations.

Advanced Applications—The long run benefits of VoIP include support formultimedia and multi-service applications, for which current telephonesystems are not equipped.

Growth in the VoIP market is expected to be considerable over the nearfuture. However, there remain many challenges facing developers of VoIPequipment, both in terms of voice quality, latency and packet loss aswell as call control and system management. The primary challenges are:the severe restrictions on acquisition and use of registered IP version4 addresses, the resulting need to use Network Address Translation (NAT)and related technologies, the limitations of existing firewalltechnologies, and the application layer requirements of VoIP protocolssuch as MEGACO, RTP, and RTCP.

The American Registry for Internet Numbers (ARIN) has placed severerestrictions on the allocation of routable, public IP addresses due tothe popular growth on the Internet, and the rapid depletion of remainingavailable addresses. In order to conserve address space, ARIN stronglyencourages end users to utilize NAT technology to conserve addressspace. The most common implementation of NAT is NAPT, or Network AddressPort Translation. This allows a single public IP address to be used tosupport thousands of hosts using private (RFC 1918) addresses. The majorproblem with NAT is that it only modifies the source IP address and portinformation in the IP header, and not anywhere in the payload. A typicalVoIP protocol uses the IP and port information of the host in thepayload for caller identification and call routing. Thus, when a MediaGateway Controller (MGC) or Trunking Gateway (TG) receives communicationfrom an end-node with conflicting information, considerable problems mayresult. Note that as used herein, the term “Trunking Gateway” refers toany device that simultaneously receives multiple analog inputs andencodes the signal into multiple corresponding IP data streams. ATrunking Gateway may also perform the reverse function of simultaneouslytaking multiple signals encoded into a multiple IP data streams andconverting it to multiple corresponding analog signals.

The NAT process is also dynamic, and so a host will be associated with aspecific port number only during the session in progress. The nextsession will almost assuredly be over a different port. This problem isexacerbated by the fact that two end nodes that need to communicatedirectly may be using the same private IP address.

Another issue relates to the firewall. Firewalls are typically designedto protect internal networks from external networks, and generally needto be aware of when sessions open and close so that the network does notremain vulnerable. Most protocols used on the Internet are TCP based,and thus the firewall can determine when sessions are opened and closedbased on SYN and FIN messages. Unfortunately, most VoIP protocols areUDP based, and therefore do not utilize SYN and FIN messages that thefirewall can detect. Complicating matters further, VoIP protocols oftenuse pairs of ports for communication, initiated from both the inside andoutside of the network. Firewalls tend to support single portcommunication only initiated from the inside. Additionally, triangulatedcommunications between IP telephones present a particular problem,referred to as the “triangle problem”, described below.

The traditional solution to an upper-layer protocol that does not workwith NAT is an Application Level Gateway (ALG). An ALG acts as a proxyby modifying the IP address and header information in the payload of thevarious protocols being used (MEGACO, RTP, RTCP) to match theinformation replaced by the standard NAT function. Additionally, the ALGtypically “negotiates” with the NAT gateway to reserve any specific portor port ranges necessary to support the protocols. This has been donefor a variety of protocols such as ICMP and FTP, and lately H.323 andSIP (two earlier VoIP standards), and solves the basic problem of publicIP to private IP communication. What are not addressed are the morecomplex interactions such as triangulated routing shown in FIG. 1. AsFIG. 1 shows, a Media Gateway Controller (MGC) 50 is coupled toApplication Level Gateway 70. The AGL 70 is coupled to two IP telephones20A and 20B, respectively. The IP telephones 20 are also coupled to oneanother directly. If IP telephone 20A contacts Media Gateway Controller50 for Call Setup through ALG 70, the MGC 50 contacts IP telephone 20B(on the same network as IP telephone 20A) through ALG 70, and IPtelephone 20B attempts to contact IP telephone 20A on the local network,the ALG 70 between IP telephones 20A and 20B must be sophisticatedenough to only correct the private address information when appropriate.

The above problem may become very complex considering that the ALG 70must maintain a local table of all internal hosts (IP telephones 20),examine the call destination address information coming from the MGC 50,and decide whether or not to modify it when routing it to the internalhosts 20. The alternative would be to route all traffic through the ALG70 regardless of whether the destination is in the internal network,perform the ALG function, then the NAT function twice, then the ALGfunction again, and then route it back out the same interface. Thisconvoluted process would be required for every single packet,introducing substantial inefficiencies to the system.

Therefore, improved systems and methods for IP telephony are desired.

SUMMARY OF THE INVENTION

The present invention includes various embodiments of a system andmethod for performing IP telephony. In one embodiment, the system mayinclude a network, at least one Media Gateway, such as an IP telephoneor Trunking Gateway, a Service Gateway, operable to couple to the MediaGateway through the network, and a Media Gateway Controller, operable tocouple to the Service Gateway and the at least one Media Gateway throughthe network.

In one embodiment, the Media Gateway may be an IP (Internet Protocol)telephone. The IP telephone may first be activated. In response, theService Gateway may negotiate a client DHCP lease with the IP telephone.The Service Gateway may use an identifier, e.g., a vendor ID, of the IPtelephone to determine a range of port numbers to assign to the IPtelephone. In other words, the Service Gateway may receive theidentifier from the IP telephone, and if the identifier is valid, assignthe port range to the IP telephone. In one embodiment, the ServiceGateway may receive a MAC ID of the IP telephone in addition to thevendor ID. The Service Gateway may determine if the MAC ID for the IPtelephone is valid, and if the MAC ID is determined to be valid, thendetermine if the identifier is valid.

The range of port numbers may include one or more port numbers which arenot reserved for use by other IP protocols. The client DHCP leasenegotiations may include the IP telephone issuing a DHCP discovermessage to the Service Gateway, which may then issue a DHCP offer to theIP telephone if the identifier is determined to be valid. The DHCP offermay include DHCP lease information based on the validated identifier,such as the range of port numbers and information indicating operationalsoftware for the IP telephone. The Service Gateway may store the DHCPlease information. The IP telephone may store the DHCP leaseinformation, and enable DHCP settings included in the DHCP leaseinformation.

The Service Gateway and the IP telephone may then operate to initializethe IP telephone. In one embodiment, the IP telephone may be initializedby executing the indicated operational software to enable IPcommunications. In one embodiment, the IP telephone may issue a requestfor the operational software, after which the Service Gateway mayprovide the operational software to the IP telephone, which may thenexecute the provided operational software to enable IP communications.In one embodiment, the IP telephone may issue a read request to a filetransfer server, e.g., a Trivial File Transfer Protocol (TFTP) Server,for the operational software, which may then provide the operationsoftware to the IP telephone. In one embodiment, the file transferserver may be included in the Service Gateway.

In one embodiment, the IP telephone may be registered by the system,e.g., by the Media Gateway Controller, prior to the Call Setup process.For example, the IP telephone may send a public IP address of the IPtelephone to the Media Gateway Controller, which may receive and storethe public IP address of the IP telephone. In one embodiment, the IPtelephone may also send a private IP address of the IP telephone to theMedia Gateway Controller, which may receive and store the private IPaddress of the IP telephone. The Media Gateway Controller may beoperable to use the public IP address and the port range to determinethe private IP address, for example, by using look-up tables.

After the registration, IP communications may be performed using the IPtelephone, using one or more ports in the range of assigned ports. Forexample, the Service Gateway may mediate IP communications between theIP telephone and an IP device, such as another IP telephone, or aTrunking Gateway, among others.

In one embodiment, performing IP communications using the IP telephonemay include the Service Gateway receiving a data packet from the IPtelephone, including a private source IP address, a source port numberin the assigned range of port numbers, and destination informationassociated with an IP device. The Service Gateway may then perform aNetwork Address Persistent Port Translation (NAPPT) on the data packet,and send the data packet to the IP device. Performing NAPPT on the datapacket may include changing the private source IP address to a publicsource IP address while leaving the source port number unchanged, andwhere the public source IP address and the source port number may beused to uniquely identify the IP telephone.

In another embodiment, performing IP communications using the IPtelephone may include the Service Gateway receiving a data packet fromthe IP device, including a public destination IP address, a destinationport number in the assigned range of port numbers, and sourceinformation, where the public destination IP address and the destinationport number may be used to uniquely identify the IP telephone. TheService Gateway may then perform a Network Address Persistent PortTranslation (NAPPT) on the data packet, and send the data packet to theIP telephone. Performing NAPPT on the data packet received from thedestination may include using the public destination IP address and thedestination port number to uniquely identify the IP telephone, andchanging the public destination IP address to a private source IPaddress of the IP telephone while leaving the destination port numberunchanged.

In one embodiment, various embodiments of the methods described abovemay be included in a memory medium. In another embodiment, variousembodiments of the methods described above may be included in aplurality of memory mediums, which may include one or more of an IPtelephone memory medium storing IP telephone program instructions, aService Gateway memory medium storing Service Gateway programinstructions, and a Media Gateway Controller memory medium storing MediaGateway Controller program instructions, where the program instructionsincluded in the plurality of memory mediums may be executable to performvarious embodiments of the methods described above.

In one embodiment, the system may include the network, two or more MediaGateways coupled through the network, as well as the Media GatewayController, coupled to the Media Gateways through the network.

In one embodiment, the Media Gateway Controller may receive a Call Setuprequest, where the Call Setup request may include a source IP addressand a destination telephone number. The Media Gateway Controller mayselect a first Media Gateway based on the source IP address, and asecond Media Gateway based on the destination telephone number.

The Media Gateway Controller may compare a public IP address of thefirst Media Gateway to a public IP address of the second Media Gateway,and if the public IP address of the first Media Gateway is the same asthe public IP address of the second Media Gateway, may select a privateIP address of the first Media Gateway and a private IP address of thesecond Media Gateway for Call Setup. Note that if the public IPaddresses of the Media Gateways are the same, then they are internal tothe system. If the public IP address of the first Media Gateway is notthe same as the public IP address of the second Media Gateway, the MediaGateway Controller may select the public IP address of the first MediaGateway and the public IP address of the second Media Gateway for CallSetup. This describes a case when a call session is between an internalIP telephone (e.g., the first Media Gateway), and an external device,such as a telephone, communicating through a Trunking Gateway (e.g., thesecond Media Gateway). Thus, in one embodiment, the first Media Gatewayand the second Media Gateway may each include one of an IP telephone ora Trunking Gateway, where the Trunking Gateway includes an interface tothe Public Switched Telephone Network (PSTN).

In one embodiment, the Media Gateway Controller may send the selected IPaddress of the first Media Gateway to the second Media Gateway, and sendthe selected IP address of the second Media Gateway to the first MediaGateway. The first Media Gateway may then send data to the second MediaGateway using the selected IP address of the second Media Gateway, andthe second Media Gateway may send data to the first Media Gateway usingthe selected IP address of the first Media Gateway.

In one embodiment, the Media Gateway Controller may register the firstand second Media Gateways prior to receiving the Call Setup request, asdescribed above. In one embodiment, registering the Media Gateways mayinclude receiving and storing the public IP address of each MediaGateway. In another embodiment, registering the Media Gateways may alsoinclude receiving and storing the private IP address of each MediaGateway.

Thus, various embodiments of the system and method described above maydistinguish between call sessions involving two internal IP telephones,and call sessions between an internal IP telephone and a TrunkingGateway, for example, interfacing with an external device, such as anexternal telephone.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention can be obtained when thefollowing detailed description of the preferred embodiment is consideredin conjunction with the following drawings, in which:

FIG. 1 illustrates an IP telephony system, according to the prior art;

FIG. 2 illustrates an IP telephony system, according to one embodimentof the present invention;

FIG. 3A is a basic Service Gateway/VPN diagram, according to oneembodiment of the present invention;

FIG. 3B is a diagram of an IP telephony network, according to oneembodiment of the present invention;

FIGS. 4A and 4B flowchart IP telephone initialization, configuration,and use, according to one embodiment;

FIGS. 5A and 5B flowchart a client DHCP lease negotiation process,according to one embodiment;

FIGS. 6A, 6B and 6C flowchart an IP telephone registration process,according to one embodiment of the invention;

FIGS. 7A, 7B and 7C flowchart a Call Setup process, according to oneembodiment of the invention;

FIGS. 8A, 8B and 8C flowchart an internal IP telephone to internal IPtelephone RTP flow, according to one embodiment of the invention;

FIGS. 9A, 9B and 9C flowchart an IP telephone to Trunking Gateway RTPflow, according to one embodiment of the invention;

FIGS. 10A and 10B flowchart an internal IP telephone to external IPtelephone RTP flow, according to one embodiment of the invention; and

FIG. 11 flowcharts a solution to the triangle problem, according to oneembodiment.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and are herein described in detail. It should beunderstood, however, that the drawings and detailed description theretoare not intended to limit the invention to the particular formdisclosed, but on the contrary, the intention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the present invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 2—A VoIP System

FIG. 2 illustrates one embodiment of a VoIP system for providing IPtelephony services to a business or other organization. The system inFIG. 2 includes one or more IP telephones 120A and 120B. As used herein,the terms “IP telephone” and “Media Gateway” are intended to include anytelephony or communication device that operates to use a networkprotocol, such as Internet Protocol (IP). Thus, an IP telephone 120 is aMedia Gateway, as is a Trunking Gateway. Said another way, an IPtelephone or Media Gateway is a device that receives an analog input andencodes the signal into an IP data stream. This device may also performthe reverse function of taking a signal encoded into an IP data streamand converting it to an analog signal. Although in the preferredembodiment, IP is the network protocol used, use of other networkprotocols is also contemplated. Note that wireless embodiments of theinvention are also contemplated. It should also be noted that in someembodiments of the VoIP system, communications may be mediated betweenan IP telephone 120 and an IP device, where the IP device may be anydevice with an interface capable of sending or receiving InternetProtocol packets, including another IP telephone.

As FIG. 2 shows, IP telephones 120A and 120B may be coupled to a ServiceGateway (SG) 170. As used herein, the term “Service Gateway” is intendedto include any system or device that operates to mediatetelecommunications, e.g., telephone calls, between the IP telephones 120(or other Media Gateways), as well as between the IP telephones 120 andexternal devices (e.g. IP devices), such as telephones on othernetworks, Trunking Gateways, or telephones or devices on the PSTN(Public Switched Telephone Network), ISDN (Integrated Services DigitalNetwork), or FDDI (Fiber Distributed Data Interface), among others.

In one embodiment, IP telephone 120A may also be coupled to IP telephone120B. The Service Gateway 170 may be coupled to a Media GatewayController (MGC) 150, as shown. In one embodiment, the IP telephones120, the Service Gateway 170, and the Media Gateway Controller 150 mayeach include software and/or hardware which implements at least aportion of an embodiment of the present invention. For example, toaddress the “triangulation” problem described above, the SG 170 mayinclude logic or software which is operable to discern an internal callfrom one which originates or terminates outside the company's network.Details of this process are described below with reference to FIGS.3A-11.

In one embodiment, the system may implement a private IP backbone usingregistered IP addresses to provide a high availability/fault tolerant IPtelephony network. The system may have a scalable design to facilitaterapid growth, and may implement capacity planning to reduce or avoidnetwork congestion. Additionally, the system may have a flexible designto support future applications. For example, it is contemplated that invarious embodiments, the system may provide support for substantiallyall access technologies. The system may further utilize trafficengineering to control data path, bandwidth allocation andlatency/jitter, such as QoS (Quality of Service), MPLS (MultipleProtocol Label Switching), RSVP (Resource Reservation Protocol), etc.,to provide an efficient, cost effective, high quality IP basedtelecommunication system.

It is further contemplated that in various embodiments, the system maybe used to provide a national, or even international, IP telephonysystem. The system may partner with local Internet Service Providers(referred to herein as Channel Partners) in each Metropolitan ServiceArea (MSA) to provide connectivity between the customer and the systemthrough a Point of Presence (PoP), i.e., a termination point forconnections to each Channel Partner, and for connections to a local PSTNnetwork.

For example, in one embodiment, the VoIP network components for each MSAmay include the Point of Presence (PoP), a Core, or regional aggregationpoint, and an App, which may include various Soft Switch elements, SS7gateways, Trunking Gateways, etc. In one embodiment, the App and theCore may be co-located. Further details of the network hardwarecomponents are presented below with reference to FIGS. 3A and 3B.

FIG. 3A—Diagram of Basic Service Gateway and VPN

FIG. 3A is a diagram of one embodiment of the present system, includingthe Service Gateway 170 and a Virtual Private Network (VPN). As FIG. 3Ashows, at least a portion of the system may be implemented on customerpremises 300. Other aspects of the system may be implemented external tothe customer premises 300, for example, in the system's PoP 350, asshown.

As indicated in FIG. 3A, components of the system present on thecustomer's premises 300 may include one or more IP telephones 120, suchas IP telephones 120A and 120B. The IP telephones 120 may each becoupled to Service Gateway 170 through an Ethernet switch 134A. TheService Gateway may couple to a customer firewall 132 through a secondEthernet switch 134B, as shown. The customer firewall 132 may couple toa customer router 130 through a third Ethernet switch 134C.

In one embodiment, the customer router 130 may be operable to couple toChannel Partner 140, which may provide access to the off-premisescomponents of the system, i.e., the VoIP PoP 350. As mentioned above,the Channel Partner 140 preferable includes an Internet Service Providerwhich is operable to provide network access, e.g., Internet access, tothe customer. The PoP portion of the system may include a PoP router 138which is operable to couple to the Channel Partner 140. The PoP router138 may couple to a VPN Concentrator 136 through Ethernet switch 134D.(A concentrator is a type of multiplexor that combines multiple channelsonto a single transmission medium in such a way that all the individualchannels can be active simultaneously.) Finally, the VPN Concentratormay be coupled to the Media Gateway Controller 150 through Ethernetswitch 134E. It should be noted that the configuration described is anexemplary embodiment, and that other configurations are contemplated.For example, in various embodiments, fewer or more Ethernet switches 134than shown may be used to implement the system.

As mentioned above, the Service Gateway 170 may include logic and/orsoftware which implements a portion of the system. It should be notedthat the SG 170 differs substantially from ALG 70 (prior art). Forexample, instead of making the SG 170 aware of the higher-levelprotocols and performing complex decisions, the SG 170 may be used for amodified NAPT function in combination with Dynamic Host ControllerProtocol (DHCP) and other services. Embodiments of each major functionare detailed below:

Hardware Platform

In one embodiment, the SG 170 may be a small form factor device, or arack mountable (19″ rack) unit, with built-in AC power supply. The SG170 may provide at least two 10 MBit Ethernet interfaces, preferably10/100 MBit. The interfaces may support 802.1q VLAN trunking. The unitmay also have SNMP management, telnet access, minimum 2 Mbytes of flashmemory, and a serial interface for command line access, as desired.

SG Addressing

The SG 170 may use a single, public IP address as the source anddestination address for IPSec VPN tunnels. This address may be sharedbetween the active and standby SGs 170. The SG 170 may use a single,public IP address to provide NAT support for all the internal hostsneeding VoIP protocol support. It may be able to use additional NATaddresses to support a large number of internal hosts, e.g., IPtelephones 120. This address may also be shared between the active andstandby SGs 170. For the internal interfaces, the SG 170 must supportvirtual IP addresses for each VLAN interface.

Routing

As a gateway and VPN device, the SG 170 may support a variety of routingfunctions. Specifically, support for numerous static routes may beprovided (e.g., at least 100). Additional routing protocol support isalso contemplated (for example, OSPF and RIP version 2). The SG 170 maybe the default gateway for all the IP telephones 120, therefore it maydetermine where traffic should be routed, and thus whether it should beNATed (or NAPPTed) and sent out a VPN interface, or routed to aninternal physical interface (Ethernet) or logical interface (VLAN).

NAT/NAPT/NAPPT

Instead of dynamically assigning ports to IP telephones, the SG 170 mayallocate a range of port numbers for each IP telephone 120 as itacquires its lease during a DHCP process, described below with referenceto FIGS. 5A and 5B. The SG 170 may maintain a table of semi-permanentmappings of the external IP address and ports to the internal hosts andports. The SG 170 may continue to replace the internal or private sourceIP address with the NATed external source IP address. It may not,however, modify the port information, though it may validate it toensure the correct internal host is using its assigned port range. SuchNetwork Address Translation may be referred to as Network AddressPersistent Port Translation (NAPPT).

DHCP

In one embodiment, the SG 170 may provide support for DHCP. The SG 170may be the DHCP server for those hosts to which it provides SG services.The SG 170 may support multiple scopes for multiple IP subnets (onesubnet for each VLAN accessed via the 802.1q trunk). Specifically, viaDHCP the SG 170 may perform one or more of the following: assign the IPaddress and network mask, set the SG 170 as the default gateway, set theDNS domain to the appropriate value, set the SG 170 as the TFTP/BOOTPserver, provide the path and file name for the boot image, and set thehost name.

In one embodiment, the SG 170 may also issue two as yet undefined DHCPoptions. As they are undefined, they may use the unassigned DHCP Optionnumbers (127-255). The SG 170 may assign a range of IP ports to each IPtelephone for its own use, and provide the IP address of the softswitch. In one embodiment, the SG 170 may inform the IP telephones 120which NAT address is being used by the SG 170 for their traffic.

In one embodiment, the DHCP service may also be able to performMAC-based reservations. For example, it may ensure an IP address is notin use before assigning it (ping verification). As another example, itmay be operable to assign addresses only to hosts with a particularclient ID (to prevent other hosts from getting addresses). In oneembodiment, the SG 170 may ignore DHCP lease requests coming from hostsnot within a MAC range. To support redundancy, the DHCP leaseinformation may be synchronized with the standby SG 170 to ensure theintegrity of every registration in the event of active SG 170 failure.

Trivial File Transfer Protocol (TFTP)

In one embodiment, the SG 170 may also act as a file transfer server,e.g., a TFTP server. The IP telephones 120 may download software, e.g.,initialization software, from the SG 170 when booting, thus, the SG 170may include memory, e.g., at least 2 Megabytes of flash memory, forstoring this initialization software. The flash on the active SG 170 maybe automatically or manually copied to the flash of the standby SG 170.

Virtual Private Network (VPN)

For security of the Call Setup and the calls in progress, as well as tosimplify the routing architecture, support for multiple IPSec (IPSecurity) VPN ESP (Encapsulating Security Payload) Tunnels may beprovided, according to one embodiment. The external interface on the SG170 may be one end of the tunnel, and the VPN Concentrator 136 may bethe other end of the tunnel (located at the PoP servicing the customer'scity). Furthermore, the ability to maintain a tunnel with a secondaryVPN Concentrator 136 and other SGs 170 within the customer's privatenetwork may be provided. The external IP address used for the VPN tunnelmay be different than the external IP address used for the NAT function.To simplify the routing architecture of the customer solution and thesystem network, the public IP addresses of the SGs 170 and the VPNConcentrator 136 that the customer uses may be from the same addressblock allocated to that customer's Internet Service Provider (ISP).

Firewall

Basic firewall functions may be provided as the SG 170 may be placedonto a public network, according to one embodiment. For performancereasons, one or more of stateful inspection, denial of serviceprotection, intrusion detection and packet filtering may be performed atline speed.

Quality of Service (QoS)

In one embodiment, to ensure the a high level of performance within thenetwork infrastructure of the customer's network and the customer'sservice provider, the SG 170 may maintain Type of Service (TOS) settingsin any IP headers traversing the device, and may “mark” all IPSectraffic exiting the device with a TOS or Differentiated Services(DiffServ) setting, thereby helping to prioritize SG traffic over othertraffic on the network.

Redundancy

Additionally, full redundancy for each function that the SG 170 performsmay be provided, according to one embodiment. In the background, theprimary SG 170 may maintain a connection state table for all NATsessions, DHCP leases, and VPN tunnels. This function may be performedvia a direct Ethernet connection, or over the internal networkinterfaces. The use of gratuitous ARP (Address Resolution Protocol) maybe used on the local interfaces in the event of fail-over to keep its IPaddresses reachable.

Additional Features:

Some additional features that are also contemplated include: support forCRTP (Compressed Real Time Protocol), a 19″ rack mountable form factor,a larger number of

Ethernet interfaces, an integrated modem, RSVP support, and MPLSsupport, among others.

SG Features Summary

A summary of features of the Service Gateway 170 is presented below. Itshould be noted that the feature list is exemplary, and is not intendedto limit the feature set of the Service Gateway 170. Rather, it iscontemplated that in various embodiments, the flexibility of the systemdesign may facilitate different or additional features to provideadvanced and future IP based telecommunication services as the relatedtechnologies develop.

Service Gateway (SG) Features:

Performance:

-   -   Wire-rate performance, total latency through the unit less than        5 msIPSec Tunnels    -   Support for 20+, wire-speed 3-DES IPSec tunnels    -   Unique IP address for each tunnel

Firewall:

-   -   Stateful inspection    -   Source/destination IP address    -   Source/destination port    -   Denial of Service protection

IP Routing:

-   -   Static routes (100+)    -   OSPF    -   RIP v.2    -   Routing across tunnels

High Availability:

-   -   Optional    -   Support for clustering or load balancing    -   OR Support for an active/standby configuration    -   Redundancy, extremely fast fail-over    -   Connection State Transfer between HA peers for all features        (NAPT, DHCP, etc.)

Interface Support:

-   -   Support for 10 Mb Ethernet, 100 Mb Ethernet, full duplex    -   Support for 802.1q and 802.1p for “outside” and “inside”        interfaces

Port Translation:

-   -   Virtual IP addresses    -   Provide basic NAT translation (private to public IP) without        changing port number    -   Support multiple NAT addresses    -   Perform NAT function before encrypting with IPSec and    -   Forwarding NAT/NAPT “before” VPN    -   Maintain persistent port mappings between internal hosts and        assigned ports

DHCP Service:

-   -   Standard features:        -   Permanent lease with updates        -   IP address        -   Mask        -   Default gateway        -   Domain name        -   Host name        -   DNS server        -   Validate address before assigning        -   MAC based reservations        -   Boot file name        -   Boot file location    -   Options:        -   Assign port ranges for host, reserved in NAPT table        -   Assign soft switch address        -   DHCP table synchronization with standby device

Additional DHCP Features:

-   -   Support multiple scopes and super-scopes    -   Support for MAC-based reservations    -   Support leasing based on class identifier (ignore requests from        non-phones)    -   Issue leases based on client identifier (Ignore requests from        non-phones)    -   Support standard DHCP options:        -   Option 1 (Subnet Mask)        -   Option 3 (Router Option)        -   Option 4 (Time Server Option)        -   Option 13 (Boot File Size Option)        -   Option 17 (Root Path)        -   Option 50 (Requested IP Address)        -   Option 54 (Server Identifier)        -   Option 66 (TFTP Server Name)        -   Option 43 (Vendor Specific Information)        -   Vendor Specific Options:            -   Assign unique port ranges to DHCP clients            -   Assign primary/backup MGC IP address            -   Assign NAT address

Traffic Engineering:

-   -   QoS/ToS    -   Integrity of TOS bits in host traffic maintained    -   Setting of TOS bits for IPSec traffic    -   RSVP    -   MPLS    -   Rate Limiting/Queuing

TFTP Service:

-   -   Support TFTP service, TFTP server    -   Storage for many images (30-100 MB)    -   Support reading and writing from IP telephones    -   Support for error logging from IP telephones

Management:

-   -   Basic SNMP    -   Tunnel specific MIBs    -   Telnet    -   Serial interface

Other SG Features:

-   -   VPN (IPSec, 3DES, manual keys, hardware encryption/decryption,        ESP tunnels)    -   Multiple simultaneous VPN tunnel terminations at wire speed        (3+tunnels)    -   CRTP support    -   BOOTP/TFTP    -   Minimum 2 MB free of flash    -   SNMP management    -   Telnet Access    -   Serial Interface    -   2×10/100 Mb Ethernet interfaces    -   Rack-mountable (19″) preferable        The VoIP IP Telephone

In one embodiment, the internal hosts, or IP telephones, may use aprivate IP address assigned by the SG DHCP service in the normal fashionfor all IP headers. Note that as used herein, the term “private IPaddress” refers to IP addresses in the ranges described in the InternetEngineering Task Force's (IETF) Request for Comment (RFC) 1918, as wellas any IP addresses that have not been assigned by any Regional InternetRegistry to the organization using the addresses. It should also benoted that as used herein, the term “public IP address” refers to any IPaddresses assigned by any Regional Internet Registry to the organizationusing the addresses.

Each IP telephone 120 may use the port numbers assigned to it by the SG170 as a part of the DHCP process. When requesting a DHCP lease, the IPtelephone 120 may specify a client identifier to differentiate itselffrom other hosts on the network. The IP telephone 120 may also know thepublic IP address to which all its traffic is being NATed, so that theIP telephone 120 may inform the soft switch during the registrationprocess, described below.

The Soft Switch

In one embodiment, the “soft switch” is actually a group of systemsrunning many applications to perform a variety of functions. Forexample, the part of the soft switch that handles the interactionbetween the IP telephones 120 and the soft switch is referred to hereinas the Media Gateway Controller (MGC) 150 (from the term used in theMEGACO standard for that interaction). The MGC 150, outside of itsstandard functions, may perform one or more special tasks in order toproperly interoperate with the IP telephones 120 and SG 170. An exampleof such a special task is described for an embodiment which uses theMEGACO protocol: when an IP telephone 120 registers with the MGC 150,the MGC 150 may store the private address of the IP telephone 120provided in the MEGACO header, as well as the NATed IP address used bythe SG 170 in the IP header; or, the IP telephone 120 may pass thatinformation along during registration. The MGC 150 may use thisinformation to determine what IP address (public or private) needs to beconveyed to the call parties, and may be particularly useful indistinguishing between Call Setup requests for two IP telephones 120 onthe same internal network, or for IP telephones on different networks.In the event that the IP telephones 120 are on the same customerpremises 300, but operating through two different SGs 170, the RTPsession may be directed to use public addresses.

VPN Concentrator

At the PoP, the VPN Concentrator may terminate the other end of the VPNtunnel initiated from the SG 170. This device may be operable to handleat least 1000 IPSec, 3DES, ESP tunnels at wire speed, and may alsosupport basic routing and firewall functions like the SG 170, as well as802.1q/p. The VPN Concentrator 136 may also provide a highly availablesolution where failure of an active device does not result in thetear-down of all existing tunnels. In the event this is not technicallyfeasible, then each SG 170 may maintain two active VPN tunnels at alltimes.

Basic VPN Concentrator Feature Summary

A summary of features of the VPN Concentrator 136 is presented below. Itshould be noted that the feature list is exemplary, and is not intendedto limit the contemplated feature set of the VPN Concentrator 136.Rather, it is contemplated that the flexibility of the system design mayfacilitate additional features to provide advanced and future IP basedtelecommunication services as the related technologies develop.

VPN Concentrator features:

Firewall

-   -   Source/destination IP address    -   Source/destination port    -   Denial of Service protection

IP Routing

-   -   Static routes (1000+)    -   OSPF    -   Routing across tunnels

High Availability

-   -   Support for clustering or load balancing    -   OR Support for an active/standby configuration    -   Redundancy, extremely fast fail-over    -   Connection State Transfer between HA peers

Interface Support

-   -   Support for 100 Mb Ethernet, Gigabit Ethernet, full duplex    -   Support for 802.1q and 802.1p for “outside” and “inside”        interfaces

Traffic Engineering

-   -   QoS/ToS    -   RSVP    -   MPLS    -   Rate Limiting/Queuing

IPSec Tunnels

-   -   Support for 1000+, wire-speed 3-DES IPSec tunnels    -   Unique IP address for each tunnel

Other Features:

-   -   CRTP support    -   Multiple simultaneous VPN tunnel terminations at wire speed        (1000 tunnels+)    -   Multiple VPN destination addresses

VPN Concentrator management features:

-   -   Basic SNMP    -   Tunnel specific MIBs    -   Telnet    -   Serial interface    -   Centralized management    -   Centralized provisioning    -   Global key management        Customer Firewall

In one embodiment, for security purposes, a customer firewall 132 mayreside on the customer premises, separating the customer's internalnetwork from external systems. The firewall 132 at the customer premisesmay be operable to support certain features in order to work inconjunction with the SG 170. If the firewall 132 does not support thesefeatures, then the SG 170 may be deployed in parallel with the firewall132, rather than behind it.

Because the SG 170 may be participating in an IPSec session, it maysource its IP packets with a public IP address and have its IP packetsremain unmodified as they pass through the firewall 132. This includesno changes to the IP header in any way, as any changes to the header maycause the IPSec traffic to be discarded by the VPN device at the otherend.

The features described above for each device in the system may providean efficient and flexible solution for VoIP telephony. Furthermore,various embodiments of the system may include an architecture thatprovides solutions for a number of problems related to theimplementation of the system in the customer environment.

The issue of unattainable addresses may be addressed by using a NAPTtechnology, as is well known in the art. Using a small number ofroutable addresses for each SG 170 is a reasonable and justifiableapproach which is consonant with the goals and methods of ARIN (AmericanRegistry for Internet Numbers). The use of VPN technologies and the useof the SG 170 as the default gateway for all the IP telephones 120 maysimplify the routing architecture of the VoIP solution. The problem ofsupporting application layer protocols that use UDP, multiple andsequential port numbers, and sessions initiated from outside the networkmay be addressed by the SG 170. The perpetual NAPT table maintained bythe SG 170 may solve the traditional problem of dynamic port numbers.The “triangulation” problem mentioned above may be solved by theintelligence in the soft switch, in combination with port rangeallocation and the NAPPT process. By implementing a DHCP solutiondedicated to the VoIP network, the customer's and service providersnetwork DHCP resources (which may be of questionable reliability) maynot be needed.

A number of specific problems related to VoIP telephony are describedbelow, as well as possible corresponding solutions provided by variousembodiments of the present invention. It should be noted that variousembodiments of the present invention may each address none, a portionof, or all of the problems listed below.

Routing Problems

Problem: it is desired that application traffic leaving the customerpremise take a predictable path, preferably the shortest path across theChannel Partner's network, with low latency and jitter. This may be achallenge because:

1) QoS technologies vary greatly in different service provider networks;

2) Channel Partners (ISPs) typically will not accept hundreds of smallroute advertisements needed to advertise (/32, /30, /29, etc.);

3) The system cannot act as a transit connection between various serviceproviders;

4) Therefore the system cannot run BGP with the Channel Partners.

Routing Solutions

1) Acquire small public IP block from each channel partner foraddressing interfaces for PoP routers;

2) Place Service Gateway at customer premise for use as default gatewayfor IP telephones;

3) Utilize VPN technology to tunnel MEGACO and RTP traffic acrosscustomer/channel partner networks;

4) Use Channel Partner IP addresses on the VPN Concentrator to ensuretraffic stays on Channel Partner network;

5) Negotiate service guarantees for VPN traffic (source/destinationaddress) from Channel Partners via appropriate traffic engineeringtechnology for their network.

Firewall Problems

Current firewall products do not support the protocols employed by thesystem, i.e. MEGACO, RTP, RTCP

The basic issues are:

1) NAPT is necessary for IP address conservation (ARIN won't provideregistered IP address for IP telephones);

2) The IP/port information is in the payload;

3) These protocols use multiple UDP ports;

4) Firewalls do not support UDP sessions well;

5) UDP sessions are initiated from the outside/untrusted network;

6) IP telephones register their IP and port numbers, expecting them tobe persistent;

7) NAPT performs dynamic allocation of ports.

Firewall Solutions

1) Bypass customer router entirely; or

2) Tunnel VPN traffic through customer firewall; this provides small“hole” in the firewall (TCP session, limited source/destination pairs),and hides all unsupported protocols from the firewall;

3) Perform NAPT function prior to encryption, so the firewall is simplyrouting the traffic through.

FIG. 3B—Diagram of IP Telephone to IP Telephone Network

FIG. 3B is a diagram of a VoIP network providing for communicationbetween IP telephones 120 of two different LANs, i.e., between IPtelephones on different customer premises. The system illustrated inFIG. 3B is effectively a bilateral implementation of the systemdescribed above with reference to FIG. 3A.

As FIG. 3B shows, IP telephones 120A and 120B may be coupled to SG 170A,which may in turn be coupled to customer firewall 132A. The customerfirewall 132A may be coupled to customer router 130A through whichaccess to Channel Partner (ISP) 170A may be provided. Thus, for acustomer A, the on-site components of the VoIP system may include the IPtelephones 120, the SG 170A, the firewall 130A, and the router 130A, aswell as other support equipment, such as one or more Ethernet switches(not shown), etc.

In one embodiment, a corresponding set of components may be present on acustomer B's premises, as shown. Specifically, IP telephones 120C and120D, SG 170B, firewall 130B, and router 130B, coupled together asdescribed above, wherein the customer router 130B may be coupled toChannel Partner (ISP) 140B.

Each customer's Channel Partner may be coupled to respective PoP routers330, which may provide access to the system PoP components. Morespecifically, the PoP router 330 coupled to Channel Partner 140A maycouple to VPN Concentrator 136A and Trunking Gateway 160A. The PoProuter 330 may further couple to Media Gate Controller 150 via anotherPoP router 330, thereby communicatively coupling IP telephones 120A and120B to the system PoP components for customer A. Similarly, the PoProuter 330 coupled to Channel Partner 140B may couple to VPNConcentrator 136B and Trunking Gateway 160B. The PoP router 330 mayfurther couple to Media Gate Controller 150 via the PoP router 330,thereby communicatively coupling IP telephones 120C and 120D to thesystem PoP components for customer B.

FIGS. 4A and 4B—IP Telephone Initialization Configuration and Use

FIGS. 4A and 4B are flowchart diagrams that illustrate initialization,configuration, and use of an IP telephone 120 (or other Media Gateway)according to one embodiment of the present invention. It is noted thatFIGS. 4A and 4B illustrate one embodiment, and that configuration andoperation of the IP telephone 120 may be performed using various othermethods according to the invention as desired. It is further noted thatvarious of the steps shown may be performed in different orders oromitted, or various additional steps may be performed as desired.

FIG. 4A flowcharts a high level IP telephony process. As shown, in step402 the IP telephone 120 may be powered on, i.e., activated. Step 402may occur when the IP telephone 120 is initially installed at the clientlocation, i.e., when it is first installed and powered on. Alternately,step 402 may be performed periodically, i.e., each morning when the userpowers on the IP telephone 120. In one embodiment, the activation of theIP telephone may be performed programmatically by software executing onthe IP telephone, an external system coupled to the IP telephone, orboth.

In step 404 client DHCP lease negotiations may be performed. Accordingto one embodiment, in step 404 the IP telephone 120 may contact theService Gateway 170 requesting a DHCP assigned IP address. In response,the client DHCP lease negotiations may be performed in step 404, where,as part of the DHCP lease negotiations, the Service Gateway 170 mayperform a TFTP transfer to the IP telephone 120 to initialize the IPtelephone 120. This may involve transferring boot and/or configurationdata to a memory, e.g., an EEPROM, located on the IP telephone 120 toconfigure or boot the IP telephone 120. In one embodiment, the TFTPprocess may include first booting the IP telephone, then loading anapplication which is executable to perform IP telephony. The client DHCPlease negotiations performed in step 404 are described in detail in theflowchart of FIGS. 5A and 5B.

In step 406 the Media Gateway Controller (MGC) 150 and the IP telephone120 may perform IP telephone 120 registration. This may involveregistering the IP telephone 120 with the MGC 150, and may includetransmitting registration information between the MGC 150 and the IPtelephone 120. One embodiment of the IP telephone registration processutilizing the MEGACO standard is described in more detail below withrespect to the flowchart of FIGS. 6A, 6B, and 6C.

In step 408 the user may login to the IP telephone 120. It is noted thatuser login may be optional, and further that the user login may actuallybe performed prior to the IP telephone registration in step 408. Afterthe user has logged in and provided any necessary password, then the IPtelephone 120 may be ready for operation or use. Thus, in step 410 theuser may place and receive calls using the IP telephone 120, where thesystem, e.g., the SG 170, may mediate IP communications between the IPtelephone and an IP device, and where the IP telephone uses at least asubset of the range of port numbers to send or receive the IPcommunications.

FIG. 4B flowcharts one embodiment of the process described above withreference to FIG. 4A in greater detail. As FIG. 4B shows, in 402, asdescribed above, the IP telephone may be powered on, then in 404 theDHCP/TFTP process may be performed. In one embodiment, the system, e.g.,the Service Gateway 170, may receive an identifier from the IP telephone120. In one embodiment, the identifier may include a Vendor Class ID.The SG 170 may then determine if the identifier is valid, and if theidentifier is valid, assign a range of port numbers to the IP telephone120 based on the identifier. The IP telephone 120 may then use at leasta subset of the range of port numbers to send or receive IPcommunications. In one embodiment, the system may also receive a MAC IDfor the IP telephone, and if the system determines that the MAC ID isvalid, the system may then determine if the IP telephone identifier isvalid. In 452, more details of the DHCP/TFTP process 404 are shown.

As indicated in 452, in one embodiment, the system may provide DHCPlease information, port range allocation, and Media Gateway Controller(MGC) information, e.g., an MGC address, to the IP telephone 120 basedon the identifier, e.g., the Vendor Class ID.

In one embodiment, the identifier of the IP telephone 120 may beincluded in a DHCP discover message issued by the IP telephone 120 tothe SG 170, in which case the SG 170 may respond with a DHCP offer tothe IP telephone (if the identifier is determined to be valid), wherethe DHCP offer may include DHCP lease information based on the validatedidentifier. The IP telephone 120 may then issue a DHCP request inresponse to the issued DHCP offer. The SG 170 and the IP telephone 120may each then store the DHCP lease information, and the IP telephone 120may enable DHCP settings included in the DHCP lease information. In oneembodiment, the DHCP lease information may include the range of portnumbers, as well as information indicating operational software for theIP telephone 120. The IP telephone 120 may then execute the indicatedoperational software to enable the IP communications. In anotherembodiment, the IP telephone 120 may issue a request for the indicatedoperational software, for example, by issuing a read request to a filetransfer server, such as a Trivial File Transfer Protocol (TFTP) server.The file transfer server may provide the operational software to the IPtelephone 120 in response to the request, and the IP telephone 120 maythen execute the operational software to enable the IP communications.

It should be noted that the port allocation preferably includesassigning a range of ports to the IP telephone 120 rather than a singleport, with the port range depending upon the identifier of the IPtelephone 120, e.g., the Vendor Class ID. For example, an IP telephone120 capable of using multiple telephone lines may be assigned a greaterrange of ports than a single line IP telephone. In one embodiment, twoports may be assigned for each two-way communication channel—one portfor incoming information, and one for outgoing information. Additionalports may be assigned for other services, such as paging, etc., suchthat a wide variety of digital telecommunication services may beprovided over the same infrastructure, including future digitaltelecommunication services not currently defined or in use. In oneembodiment, the range of port numbers assigned to the IP telephone 120may include ports which are not reserved for use by other IP protocols,such as FTP, HTTP, etc., by the Internet Engineering Task Force (IETF).

As described above with reference to FIG. 4A 404, the method may furtherinclude downloading initialization information to the IP telephone 120via TFTP.

In 406, client registration may be performed, as explained in greaterdetail in 462-466. In 462, the IP telephone 120 may register with theMGC 150 using the assigned port range received from the DHCP lease of404 above. Note that the IP telephone 120 may contact the MGC 150 usingthe MGC information (e.g., an address of the MGC 150) provided in 452above. Then, in 464 the Service Gateway 170 (as a NAT service) maychange the IP source address, e.g., from private to public, but leavethe port information unmodified. In 466, the MGC 150 may register the IPtelephone 120 using public IP and port information of the IP telephone,i.e., registration information of the IP telephone. In one embodiment,the registration information may also include private IP information ofthe IP telephone. In other words, the MGC 150 may also use private IPinformation (e.g., the private IP address) of the IP telephone toregister the IP telephone. It should be noted that in one embodiment,the MGC 150 may store the received registration information for use inCall Setup, described below.

It should be noted that in one embodiment the process described in480-494 below substantially describes the process described in 408 and410 of FIG. 4A, wherein a user optionally logs in to the system, thenplaces or receives telephone calls. In 480, a Call Setup process may beperformed. In particular, in 482 the IP telephone 120 may initiate acall via MEGACO signaling to the MGC 150 using the assigned port rangeand MGC address received from the DHCP lease in 404 above. In 484 theService Gateway 170 (as a NAT service) may change the IP source address,e.g., from private to public, but leave the port information unmodified.Then, in 486 the MGC 150 may signal the call destination, e.g., an IPdevice, using public IP, private IP, and/or port information.

In 490, RTP flow related to the IP telephone call may be managed. Forexample, as indicated in 492, in one embodiment, the IP telephones mayexchange RTP using one or more ports from the assigned port rangereceived from the DHCP lease of 404 above. Then, as described above in464 and 484, in 494, the Service Gateway 170 (as a NAT service) maychange the IP source address, e.g., from private to public, leaving theport information unmodified. More specifically, the SG 170 may receive adata packet from the IP telephone 120, perform a network addresspersistent port translation (NAPPT) on the data packet, and send theNAPPTed data packet to a destination IP device. As mentioned above, thedata packet may include a private source IP address of the IP telephone120, a source port number (from the IP telephone's assigned range ofport numbers), and destination information associated with the IPdevice. In one embodiment, performing a NAPPT on the data packet mayinclude changing the private source IP address to a public source IPaddress while leaving the source port number unchanged, and where thepublic source IP address and the source port number may be used touniquely identify the IP telephone 120.

Conversely, when the SG 170 receives a data packet from the IP devicedestined for the IP telephone 120, the data packet may include a publicdestination IP address, a destination port number; and sourceinformation associated with the IP device, where the destination portnumber is in the assigned range of port numbers for the IP telephone120. In one embodiment, the public destination IP address and thedestination port number may be used to uniquely identify the IPtelephone 120. Performing a NAPPT on the data packet may include usingthe public destination IP address and the destination port number touniquely identify the IP telephone 120, and changing the publicdestination IP address to a private destination IP address while leavingthe destination port number unchanged. Note that in this embodiment, theprivate IP address may be an IP address of the IP telephone 120. AfterNAPPTing the data packet, the SG 170 may send the data packet to the IPtelephone 120.

Thus, in the above process, the SG 170 may facilitate and mediate the IPtelephony process by assigning a range of ports to a client IPtelephone, and by NAPPTing packet IP source/destination addresses whileleaving the corresponding port information unchanged. These features mayallow for a great deal of flexibility and future expansion of thesystem, while addressing the “triangle” problem of distinguishingbetween internal and external IP telephone connections.

Each of these sub-processes is described in greater detail below withreference to FIGS. 5A-10B.

FIGS. 5A and 5B—Client DHCP Lease Negotiations

FIGS. 5A and 5B illustrates one embodiment of client DHCP leasenegotiations performed in 404 above, according to one embodiment of theinvention. It is noted that FIGS. 5A and 5B illustrate one exemplaryembodiment of these lease negotiations, and that these negotiations maybe performed in various manners according to the present invention. Itis further noted that various of the steps shown may be performed indifferent orders or omitted, or various additional steps may beperformed as desired.

As shown, in step 502 the client IP telephone 120 may begin execution ofa boot application. This may involve beginning execution of anapplication stored on a memory on the IP telephone 120 such as anEEPROM.

In step 504 the IP telephone 120 may determine if an IP address or IPinformation has been statically assigned. If IP information has beenstatically assigned as determined in step 504, then operation mayproceed to step 542, described below. If IP information is determined tonot be statically assigned in step 504, then in step 506 the client IPtelephone 120 may issue a DHCP discover command, including a classidentifier, e.g., a Vendor Class Identifier. This DHCP discover requestoperates to request a DHCP dynamically assigned IP address.

In step 508 the server, e.g., the Service Gateway 170, may receive theDHCP discover command. In step 510 the Service Gateway 170 may determineif the Mac ID of the IP telephone 120 is valid. If not, then operationmay proceed to step 534, described below. If the Mac ID is determined tobe valid in step 510 then in step 512 the Service Gateway 170 maydetermine if the identifier, e.g., the Vendor Class ID, is valid. If theVendor Class ID is not valid then operation may proceed to step 532,described below.

If the Vendor Class ID is determined to be valid in step 512, then instep 514 the server, i.e., the Service Gateway 170 may issue a DHCPoffer with lease information. In step 516 the client may receive theDHCP offer. As described above, in one embodiment, the DHCP offer mayinclude DHCP lease information for the IP telephone 120.

In step 518 the IP telephone 120 may determine whether the leasecontains all the necessary options for operation of the IP telephone120. If the lease is determined to not contain all the necessary optionsas determined in step 518, then in step 520 the IP telephone 120 mayignore the DHCP offer and operation may proceed to step 538.

In step 538 the IP telephone 120 may wait for a period of time, e.g., await interval, and then reissue a DHCP discover command with VendorClass ID in step 506, and the above operation may repeat.

If the MAC ID is determined to not be valid in step 510, then in step534 the Service Gateway 170 may ignore the DHCP discover command, i.e.,no DHCP offer may be provided, and in 536 the client may not receive anyDHCP offer.

If the Vendor Class ID is determined to not be valid in step 512, thenin step 532 the Service Gateway 170 may ignore the DHCP discover commandand in step 536 the client accordingly may not receive any DHCP offer.In either instance after any of steps 532 or 536, if the IP telephone120 does not receive a DHCP offer after a certain period of time, i.e.,after the wait interval in step 538, then in step 506 the client mayreissue a DHCP discover command with the Vendor Class ID, and the aboveoperation may repeat.

If in step 518 the IP telephone 120 determines that the lease doescontain all the necessary options, then in step 522 the client may issuea DHCP request. After issuing the DHCP request in step 522, theoperation may proceed to step 562 of the flowchart, described below.

If in step 504 the client IP telephone 120 determines that the IPinformation is statically assigned, then operation may proceed to step542. As shown, in step 542 the client IP telephone 120 may determinewhether the boot image is local, i.e., if the operational software forthe IP telephone is stored locally. If the boot image is determined tobe local in step 542, then in step 590 the client may execute the bootimage to boot up the IP telephone, and then termination may occurwherein the operation completes.

If the boot image is determined to not be local in step 542, then instep 544 the client may begin Trivial File Transfer Protocol (TFTP)activity. In step 546 the client may issue a RRQ (e.g., a read request)to a TFTP server preferably using the address supplied by the DHCP. Instep 548 the TFTP server may receive the RRQ (opcode 1). In step 550 theTFTP server may determine if the file is in the local flash. If so, thenin step 552 the TFTP server may issue an acknowledge to the client IPtelephone 120 (opcode 4) and in step 554 the client IP telephone 120 maystore the image in memory. In other words, in step 554 the TFTP servermay transfer the image to the client IP telephone, and the client IPtelephone 120 may store this image in the memory.

In step 556 the client IP telephone 120 may determine whether thetransfer has finished or completed. If so, then the client IP telephone120 may execute the boot image received and stored in step 554, andoperation may terminate or complete.

If the IP telephone 120 determines that the transfer has not completedin step 556, then operation may proceed to step 582. In step 582 if theTFTP has been attempted more than some other specified threshold (e.g.,four times), then the client IP telephone 120 may error out of TFTPactivity in step 584 and operation may proceed to step 502. If TFTPtransfer has not been attempted more than four times, then operation mayproceed to step 546, and the above operations may repeat.

If the TFTP server determines that the file is not in the local flash instep 550, then in step 580 the TFTP server may issue a file not founderror to the client IP telephone 120 (output 5 error code 1) andoperation may proceed to step 582.

After the client issues the DHCP request in step 522, then operation mayproceed to step 562 as noted above. In step 562 the server may receivethe DHCP request. In step 564 the server may store the lease inpersistent data, i.e., store the lease in a nonvolatile memory on theserver. In step 566 the server may issue a DHCP acknowledge (DHCP ACK).In step 568 the client may receive the DHCP acknowledge. In step 570 theclient may store the lease information received from the server. In step572 the client may enable the lease values (i.e., DHCP settings)received. In step 574 the client may ignore any further DHCPacknowledges and operation may proceed to step 542. The leaseinformation in step 570 may include a private IP address and other leaseinformation which enables operation of the IP telephone 120 on the localnetwork of the client system.

Thus, in the DHCP lease negotiation and registration, the IP telephonemay be assigned a range of ports for use, depending upon the IPtelephone's Vendor Class ID. For example, an IP telephone capable ofusing multiple telephone lines may be assigned a greater range of portsthan a single line IP telephone. In the preferred embodiment, two portsare assigned for each two-way communication channel—one port forincoming information, and one for outgoing information. Additional portsmay be assigned for other services, such as paging, etc., such that awide variety of digital telecommunication services may be provided overthe same infrastructure. The system may distinguish between internalcall connections and external call connections by examining theinformation associated with the IP telephone(s) involved with the call.

FIGS. 6A, 6B and 6C—IP Telephone Registration Process

FIGS. 6A, 6B and 6C flowchart the IP telephone registration process of406 described with reference to FIGS. 4A and 4B above, according to oneembodiment. This particular embodiment uses the MEGACO standard,although other protocols and standards may be implemented as desired. Itis further noted that various of the steps shown may be performed indifferent orders or omitted, or various additional steps may beperformed as desired.

As shown, after the DHCP/TFPP process 404 is completed, then in step 602the client may begin the registration process.

In step 604 the system may determine if an IP port is available forregistration. If an IP port is not available for registration then instep 606 the registration may fail and the process may terminate.

If an IP port is available for registration then in step 608 the systemmay determine if the Media Gateway Controller address is provided byDHCP. If the MGC address was not provided by DHCP then again in step 606the registration may fail and the process may terminate.

If the MGC address was provided by DHCP then in step 610 the client mayselect a port number for MEGACO. Then in step 612 the client may selecta primary MGC address to register.

In step 614 the client may transmit a Service Change command to the MGC150. An example packet header is shown as part of 614, comprising asource IP address, denoted as Private, a source port, selected from theassigned port range as indicated, a destination IP address, here shownas the Primary MGC address, and a destination port, here shown with anarbitrary example value of 55555. In step 616 the Service Gateway (SG)170 may receive the request. Then in step 618 the system, e.g., the SG,may determine if the IP destination is internal or external, i.e.,remote.

If the IP destination is determined to be internal then in step 620 thedata (packet) may be forwarded out the local interface, and in step 622the packet may be dropped.

In step 624 the telephone may time out on the request. Then in step 626the system may determine if use of a secondary MGC address has beenattempted, and if a secondary has been attempted then in step 606 theregistration may fail and the process may terminate. If a secondary hasnot been attempted then in step 628 the client may select a secondaryMGC address to register and the process may continue again at step 614as described above.

Referring back to step 618, if the IP destination is determined to beexternal, then in step 634 the Service Gateway 170 may select adestination tunnel based on the destination IP address. Then in step 636the system may determine if the selected tunnel is operational. If thetunnel is not operational then in step 622 the packet may be dropped andthe process may continue with step 624 as previously described.

If the tunnel is operational then in step 638 the Service Gateway 170may perform Network Address Persistent Port Translation or NAPPT. Asindicated, the packet header information at this stage may change in thefollowing way: the source IP address may be changed from Private toPublic, while the source port remains UNCHANGED; the destination IPaddress remains set to the primary MGC address; and the destination portretains the example value 55555.

Then in step 640 the Service Gateway 170 may perform IP securityencryption on the packet. As shown, the original packet is encapsulatedin a new packet with a source address of the external interface addressof the Service Gateway, and the destination address of the VPNConcentrator. The Service Gateway 170 may forward the data (packet) overthe selected tunnel.

In step 646 the traffic may traverse the channel partner network, i.e.,the network provided by an Internet Service Provider (ISP). After thedata traffic (packet) has traversed the channel partner network then instep 648 the data traffic may reach a virtual private networkconcentrator or VPN Concentrator 136.

In step 650, the VPN Concentrator 136 may decrypt the data traffic, and,as shown in step 652, may route the data traffic to a local router. Asshown, in one embodiment, the data packet header information at thispoint may include a source IP address, indicated as Public, a sourceport which remains UNCHANGED, as shown, a destination IP address set tothe primary address of the MGC, and a destination port with the examplevalue of 55555.

In step 654 the local router may forward the data traffic to the MGC150, then, in step 656 the system may determine if the MGC 150 receivesthe data, i.e., responds to Address Resolution Protocol (ARP). If theMGC 150 does not receive the data then the process may drop the packetin step 622, and continue as described above.

If the MGC 150 does receive the packet, i.e., does respond to the ARP,then in step 658 the MGC 150 may process the registration. In step 660the MGC 150 may store the information in response to the registration.One example of the stored information is shown as part of 660,comprising the IP telephone IP address, denoted as SG Public, referringto the Service Gateway's public IP address for the telephone 120, theMEGACO port, indicated here as UNCHANGED, and the SG IP, indicated as SGPublic.

In step 662 the MGC 150 may reply with a Service Change. This mayinvolve sending a packet back to the source IP telephone, and so, as 662shows, in one embodiment, the packet header for the data now may nowinclude the source IP address and port set to the Primary MGC addressand the example value 55555, i.e., the prior packet's destinationinformation described in 614 above. As indicated, the destinationinformation may include the destination IP address set to the SG publicaddress, and the destination port remaining UNCHANGED. In step 664 alocal router may forward the traffic to the VPN Concentrator 136. Instep 666 the VPN Concentrator 136 may perform IP security encryption. Instep 668 the VPN Concentrator 136 may route the data to another localrouter. Then in step 670 the data may traverse the channel partnernetwork, i.e., the network provided by the ISP.

In step 672 the data may reach the Service Gateway 170. The ServiceGateway 170 may then decrypt the data as indicated in step 674. In step676 the Service Gateway 170 may then perform Network Address PersistentPort Translation (NAPPT). As step 676 shows, the packet headerinformation may be modified such that the source IP address is set tothe primary MGC address, the source port is set to the example value55555, the destination IP address is changed from Public to Private, andthe destination port remains UNCHANGED. Then in step 678 the SG mayforward the data out through the local interface.

In step 680 the system may determine of the telephone responds to theaddress resolution protocol, i.e., may determine if the telephonereceives the data. If the telephone does not receive the data, then theprocess may proceed with step 624, described above. If the telephonedoes receive the data, then in step 682 the telephone 120 may processthe registration.

In step 684 the system may determine if the registration information isvalid. If the registration information is invalid, then the registrationmay fail, as indicated in 606, and the process may terminate.

If the registration information is valid, then in step 686 MEGACOregistration process exchange continues until the data exchange iscomplete. The process may then terminate, as shown.

Thus, the Service Gateway 170 may mediate a remote registration processbetween a client using an IP telephone 120 and a Media GatewayController 150 which performs the registration.

One of the benefits of the present system is that the customer's systemcomponents may be configured and/or reconfigured remotely by downloadingnew software from the system, i.e., complex on-site servicing forservice upgrades or modifications may be reduced or eliminated by thepresent system and method.

FIGS. 7A, 7B and 7C—IP Telephone Client Call Setup Process

FIGS. 7A, 7B and 7C flowchart a client Call Setup process, according toone embodiment of the invention. As shown, the Call Setup processpreferably occurs after the DHCP/TFTP process 404 and the clientregistration process 406, described above. It should be noted that thisparticular embodiment uses the MEGACO standard, although other protocolsand standards may be implemented as desired. It is further noted thatvarious of the steps shown may be performed in different orders oromitted, or various additional steps may be performed as desired.

In step 702, the client call may begin. In the preferred embodiment, thecall may be initiated by a client activating the IP telephone 120, e.g.,by picking up the receiver, and dialing a destination telephone number.

In step 704, the system may determine if an IP port is available forMEGACO, and if an IP port is not available, then in step 706 the CallSetup may fail and the process may terminate.

If an IP port is available, then in 708 the system may determine if aMedia Gateway Controller (MGC) address was provided by DHCP. If the MGCaddress was not provided, then the Call Setup may fail, as indicated instep 706, and the process may terminate.

If the MGC address was provided by DHCP, then in step 710 the client mayselect a port number for MEGACO signaling. In the preferred embodiment,the port number may be selected from the range of port numbers assignedto the IP telephone client in the DHCP lease negotiation process 404, asdescribed above with reference to FIGS. 5A and 5B.

In step 712 the client may select a primary MGC address to contact, andin step 714, may transmit a Service Change command to the MGC 150. Anexample packet header is shown as part of 714, comprising a source IPaddress, denoted as Private, a source port, selected from the assignedport range, as indicated, a destination IP address, here shown as thePrimary MGC address, and a destination port, here shown with anarbitrary example value of 55555.

In step 716 the Service Gateway (SG) 170 may receive the Service Changecommand or request. Then, in 718, the SG 170 may determine if the IPdestination is local or remote. The terms “local” and “remote” refer tocall destinations in the customer network which are inside, or outside,respectively, of the originating IP telephone's IP subnet. In otherwords, if the destination is local, then the call may be sent directlyto the destination IP telephone 120, without having to be transmittedthrough a Service Gateway 170.

If the IP destination is local, then in step 720 Call Setup data may beforwarded out the local interface, and in step 722, the packet may bedropped. Then, in step 724, after a suitable waiting period, the IPtelephone 120 may time out on the request.

After the IP telephone 120 times out on the request, then in 726 thesystem may determine if a secondary has been attempted, i.e., if asecondary MGC address has been tried.

If a secondary MGC address has been attempted, then the Call Setup mayfail, as indicated in step 706, and the process may terminate.

If a secondary MGC address has not been attempted, then in 728 theclient may select a secondary MGC address to contact, and the processmay continue with step 714, as described above.

Referring back to step 718, if the IP destination is determined to beremote, then in 734 the Service Gateway 170 may select a destinationtunnel based on the destination IP address.

In step 736 the system may determine if the selected tunnel isoperational. If the tunnel is not operational, then the packet (CallSetup data) may be dropped, as indicated in 722, and the process maycontinue as described above.

If the tunnel is operational, then in step 738 the Service Gateway 170may perform Network Address Persistent Port Translation (NAPPT) on theCall Setup data. As indicated, the packet header information at thisstage may change in the following way: the source IP address may bechanged from Private to Public, while the source port remains UNCHANGED;the destination IP address may remain set to the primary MGC address;and the destination port may retain the example value 55555.

In step 740 the Service Gateway 170 may perform IP Security (IPSec)encryption on the Call Setup data. In one embodiment, the packet headerinformation may include the following changes: the source IP address maybe set to a Public NAT address, and the destination IP address may beset to the VPN Concentrator. The source and destination port informationmay remain unchanged.

In step 744, the Service Gateway 170 may forward the Call Setup dataover the selected tunnel. The Call Setup data may then traverse thechannel partner network, e.g., the network of an ISP, as indicated instep 746.

In step 748, the Call Setup data may reach a Virtual Private Network(VPN) Concentrator 136, which may decrypt the Call Setup data as shownin step 750. Then, in step 752, the VPN Concentrator 136 may route theCall Setup data to a local router. As shown, in one embodiment, the datapacket header information at this point may include a source IP address,indicated as Public, a source port which remains UNCHANGED, as shown, adestination IP address set to the primary address of the MGC, and adestination port with the example value of 55555.

Then, the local router may forward the Call Setup data to the MGC 150,as indicated in step 754.

In step 756, the system may determine if the MGC 150 responds to AddressResolution Protocol (ARP), i.e., if the MGC 150 receives the Call Setupdata. If the MGC 150 does not receive the Call Setup data, then in step722, the packet (Call Setup data) may be dropped, and the process maycontinue as described above.

If the MGC 150 does receive the Call Setup data, then in step 758 theMGC 150 may process the Call Setup request, and in step 760, may replywith a Service Change. In one embodiment, the packet header for the datanow may now include the source IP address and port set to the PrimaryMGC address and the example value 55555. As indicated, the destinationinformation may include the destination IP address set to the SG publicaddress, and the destination port remaining UNCHANGED.

In step 762, a local router may forward the Call Setup data to the VPNConcentrator 136, which may perform IPSec encryption on the data, asindicated in step 764. The VPN Concentrator 136 may then route the CallSetup data to a local router, as shown in step 766.

In step 768 the Call Setup data may traverse the channel partnernetwork, i.e., the network of the ISP, and in step 770, may reach theService Gateway 170. In step 772 the Service Gateway 170 may decrypt theCall Setup data, then perform Network Address Persistent PortTranslation (NAPPT), as shown in step 774. The packet header informationmay be modified such that the source IP address is set to the primaryMGC address, the source port is set to the example value 55555, thedestination IP address is changed from Public to Private, and thedestination port remains UNCHANGED.

The SG 170 may then forward the Call Setup data out the local interface,as indicated in step 776.

In step 778, the system may determine if the IP telephone 120 respondsto Address Resolution Protocol (ARP), i.e., receives the Call Setupdata. If the IP telephone 120 does not receive the Call Setup data, thenthe process may continue with step 722, as described above. If the IPtelephone 120 receives the Call Setup data, then in 780 the IP telephone120 may process the information, i.e., the Call Setup data.

In step 782, the IP telephone may determine if the Call Setupinformation is valid. If the Call Setup information is not valid, thenin 706 the Call Setup may fail, and the process may terminate. If theCall Setup information is valid, then in step 784 the MEGACO exchangeprocess exchange may continue until data exchange is complete, and theprocess may terminate.

FIGS. 8A, 8B and 8C—Internal IP Telephone To Internal IP Telephone RTPFlow

FIGS. 8A, 8B, and 8C flowchart Real-Time Transport Protocol (RTP) dataflow between a first internal IP telephone 120A and a second internal IPtelephone 120B, related to a call initiated by the first internal IPtelephone 120A. RTP is an Internet Protocol for transmitting real-timedata such as audio and video. RTP itself does not guarantee real-timedelivery of data, but it does provide mechanisms for the sending andreceiving applications to support streaming data. Typically, RTP runs ontop of the UDP protocol, although the specification is general enough tosupport other transport protocols. It is noted that FIGS. 8A, 8B, and 8Cillustrate one exemplary embodiment of data flow, and that this flow mayoccur in various manners according to the present invention. It isfurther noted that various of the steps shown may be performed indifferent orders or omitted, or various additional steps may beperformed as desired.

As shown, the RTP call process preferably occurs after the DHCP/TFTPprocess 404, the client registration process 406, and the Call Setupprocess 480, described above with reference to FIGS. 5A-7C.

In step 802, IP telephone 120A may begin an RTP call to IP telephone120B. As noted above, in this embodiment, both IP telephones 120 areinternal to the local network.

In step 804 the system may determine if the MGC 150 provided adestination IP address and port. If the MGC 150 did not provide adestination IP address and port, then in step 806 the session mail fail,and the process may terminate. If the MGC 150 did provide a destinationIP address and port, then in step 808, the system may determine if theIP address is local or remote. The terms “local” and “remote” refer tocall destinations in the customer network which are inside, or outside,respectively, of the originating IP telephone's IP subnet. In otherwords, if the destination is local, then the call may be sent directlyto the destination IP telephone 120, without having to be transmittedthrough a Service Gateway 170.

If the IP address is remote, then in step 810 the IP telephone 120A maytransmit an RTP packet to Service Gateway (SG) 170A, which may receivethe packet in step 812, and select a destination tunnel based on thedestination IP address, as indicated in step 814.

In step 816, the SG 170A may determine if the destination tunnel isoperational. If the destination tunnel is not operational, then in 818,the SG 170A may determine if an alternate tunnel is operational. If noalternate tunnel is available, then in step 820 the packet may bedropped, the session may fail, as indicated in step 806, and the processmay terminate.

If an alternate tunnel is available, then the process may continue withstep 822, described below.

Referring back to step 816, if the destination tunnel is operational,then in step 822 the SG 170A may determine if the data in thedestination tunnel should be NATed, i.e., if Network Address Translationshould be performed on the data. Note that if the data should be NATed,then the packet may be assumed to have an external destination, and sohas been inappropriately routed to the wrong interface (local).Therefore, if NAT is to be performed, then in step 824 the call may faildue to invalid IP information, the session may fail, as indicated instep 806, and the process may terminate.

If the destination tunnel does not need to be NATed, then in step 826the SG 170A may perform IPSec encryption on the data (packet), andforward the data over the selected tunnel, as indicated in step 828. Instep 830, the data may traverse the customer network, and may reach asecond Service Gateway 170B, as shown in step 832.

In step 834, the SG 170B may decrypt the data, and in step 836, may ARPfor the IP telephone 120B. In step 838, the system may determine if theIP telephone 120B responds to the ARP. If the IP telephone 120B does notrespond to the ARP, then in step 840 the packet may be dropped, thesession may fail, as indicated in step 842, and the process mayterminate.

If the IP telephone 120B responds to the ARP, then in step 844 the SG170B may forward the data to IP telephone 120B. In step 846, the IPtelephone 120B may reply with an RTP packet to IP telephone 120A. Instep 848, the system may determine if the RTP session succeeded. If theRTP session did not succeed, then the session may fail, as indicated instep 842, and the process may terminate.

If the RTP session succeeded, then in step 850, the RTP exchange maycontinue until data exchange is complete.

Referring back to step 808, if the IP address is determined to be local,then in step 852 the IP telephone 120A may ARP for IP telephone 120B.

In step 854, the system may determine if the IP telephone 120B respondsto the ARP. If the IP telephone 120B does not respond to the ARP, thenin step 840 the packet may be dropped, the session may fail, asindicated in step 842, and the process may terminate.

If the IP telephone 120B responds to the ARP, then in step 856 IPtelephone 120A may transmit the RTP packet to IP telephone 120B. Anexample packet header is shown as part of 856, comprising a source IPaddress, denoted as Phone 1 Private, a source port, selected from theassigned port range during the Call Setup process 480, as indicated, adestination IP address, here shown as Phone 2 Private indicated by MGCduring Call Setup process, and a destination port, shown as Phone 2 portindicated by MGC during Call Setup Process.

In step 858, the IP telephone 120B may receive the RTP packet, and instep 846, the IP telephone 120B may reply with an RTP packet to IPtelephone 120A. In one embodiment, the packet header may now include asource IP address, denoted as Phone 2 Private, a source port, selectedfrom the assigned port range during the Call Setup process 480, asindicated, a destination IP address, here shown as Phone 1 Privateindicated by MGC during Call Setup process, and a destination port,shown as Phone 1 port indicated by MGC during Call Setup Process.

In step 848, the system may determine if the RTP session succeeded. Ifthe RTP session did not succeed, then the session may fail, as indicatedin step 842, and the process may terminate.

If the RTP session succeeded, then in step 850, the RTP exchange maycontinue until data exchange is complete, at which time the process mayterminate.

Thus, in one embodiment, internal IP telephone calls within the same IPsubnet may be transmitted directly between IP telephones 120, while IPtelephone calls made between internal IP telephones 120 in different IPsubnets may be routed through Service Gateways 170.

FIGS. 9A, 9B and 9C—IP Telephone To Trunking Gateway RTP Flow

FIGS. 9A, 9B, and 9C flowchart RTP data flow from an IP telephone 120 toa Trunking Gateway 160 related to a client initiated IP telephone call.It is noted that FIGS. 9A, 9B, and 9B illustrate one exemplaryembodiment of data flow, and that this flow may occur in various mannersaccording to the present invention. It is further noted that various ofthe steps shown may be performed in different orders or omitted, orvarious additional steps may be performed as desired.

As shown, the RTP call process preferably occurs after the DHCP/TFTPprocess 404, the client registration process 406, and the Call Setupprocess 480, described above with reference to FIGS. 5A-7C.

In step 902, the client may begin an RTP call. In the preferredembodiment, the client initiates the call through IP telephone 120.

In step 904 the system may determine if the MGC 150 provided adestination IP address and port. If the MGC 150 did not provide adestination IP address and port, then in step 906 the session mail fail,and the process may terminate. If the MGC 150 did provide a destinationIP address and port, then in step 908, the client may transmit an RTPpacket to the destination Trunking Gateway (TG) 160. An example packetheader is shown as part of 908, comprising a source IP address, denotedas Phone 1 Private, a source port, selected from the assigned port rangeduring the Call Setup process 480, as indicated, a destination IPaddress, here shown as TG Public indicated by MGC during the Call Setupprocess, and a destination port, shown as TG port indicated by MGCduring the Call Setup process.

In step 910, Service Gateway 170 may receive the RTP packet, and in step912, may determine if the IP destination is local or remote. If the IPdestination is determined to be local then in step 914 the data (packet)may be forwarded out through the local interface, in step 906 thesession may fail, and the process may terminate.

If the IP destination is remote, then in step 916, the SG 170 may selecta destination tunnel based on the destination IP address. In step 918,the SG 170 may determine if the destination tunnel is operational. Ifthe destination tunnel is not operational, then in 920, the SG 170 maydetermine if an alternate tunnel is available. If no alternate tunnel isavailable, then in step 922 the packet may be dropped, the session mayfail, as indicated in step 906, and the process may terminate.

If an alternate tunnel is available, then the process may continue withstep 924, described below.

Referring back to step 918, if the destination tunnel is operational,then in step 924 the SG 170 may perform NAPPT (Network AddressPersistent Port Translation) on the data. In one embodiment, the packetheader information may be modified such that the source IP address isset from Phone 1 Private to Phone 1 Public, the source port remainsUNCHANGED, the destination IP address is set to the TG Public address,and the destination port as indicated by the TG.

In step 926, the SG 170 may perform IPSec encryption on the data. In oneembodiment, the packet header information may include the followingchanges: the source IP address is set to a Public NAT address, and thedestination IP address is set to that of the VPN Concentrator. Thesource and destination port information may remain unchanged.

In step 928, the SG 170 may forward the data over the selected tunnel.Then, in step 930, the data may traverse a channel partner network,i.e., the network of an ISP, and in step 932 the data may reach a VPNConcentrator 136. The VPN Concentrator 136 may decrypt the data, asindicated in step 934, then, in step 936, may forward the data to alocal router.

In step 938 the data may reach the TG 160. In step 940, the system maydetermine if the TG 160 receives the data. If the TG 160 does notrespond to the data, then the packet may be dropped, as indicated instep 922, the session may fail in step 906, and the process mayterminate.

If the TG 160 does receive the data, then in step 942, the TG mayprocess the RTP data. In step 944, the system may determine if the TG160 responds. If the TG 160 does not respond, then the session may fail,as indicated in step 906, and the process may terminate.

If the TG 160 does respond, then the system may determine if the RTPsession succeeds, as indicated in step 946. If the RTP session doessucceed, then in step 948, the RTP exchange may continue until dataexchange is complete, and the process may terminate.

FIGS. 10A and 10B—IP Telephone to External IP Telephone RTP Flow

FIGS. 10A and 10B flowchart RTP data flow between an internal IPtelephone 120A and an external IP telephone 120C, related to a callinitiated by the first internal IP telephone 120A. It is noted thatFIGS. 10A and 10B illustrate one exemplary embodiment of data flow, andthat this flow may occur in various manners according to the presentinvention. It is further noted that various of the steps shown may beperformed in different orders or omitted, or various additional stepsmay be performed as desired.

As shown, the RTP call process preferably occurs after the DHCP/TFTPprocess 404, the client registration process 406, and the Call Setupprocess 480, described above with reference to FIGS. 5A-7C.

In step 1002, IP telephone 120A may begin an RTP call to an external IPtelephone 120C.

In step 1004 the system may determine if the MGC 150 provided adestination IP address and port. If the MGC 150 did not provide adestination IP address and port, then in step 1006 the session mailfail, and the process may terminate. If the MGC 150 did provide adestination IP address and port, then in step 1008, the client maytransmit an RTP packet to the destination telephone, i.e., IP telephone120C. In one embodiment, the packet header for the data now may includethe source IP address set to Phone 1 Private, the RTP port set to theport selected during the Call Setup process, the destination IP address,set to Phone 2 Public indicated by the MGC during the Call Setupprocess, and the destination port, set to Phone 2 port indicated by theMGC during the Call Setup process.

In step 1010, the Service Gateway (SG) 170 may receive the RTP (packet),and in step 1012, may determine if the IP destination is local orremote. The terms “local” and “remote” refer to call destinations in thecustomer network which are inside, or outside, respectively, of theoriginating IP telephone's IP subnet. In other words, if the destinationis local, then the call may be sent directly to the destination IPtelephone 120, without having to be transmitted through a ServiceGateway 170.

If the IP destination is local, then in step 1014 the packet may beforwarded out through the local interface, the session may fail, asindicated in 1006, and the process may terminate.

If the IP address is determined to be remote, then in step 1016 the SG170 may select a destination tunnel based on the destination IP address.

In step 1018, the SG 170 may determine if the destination tunnel isoperational. If the destination tunnel is not operational, then in 1020,the SG 170 may determine if an alternate tunnel is available. If noalternate tunnel is available, then in step 1022 the packet may bedropped, the session may fail, as indicated in step 1006, and theprocess may terminate.

If an alternate tunnel is available, then the process may continue withstep 1024, described below.

Referring back to step 1016, if the destination tunnel is operational,then in step 1024 the SG 170 may perform NAPPT on the call data, i.e.,the packet. In one embodiment, the packet header information may bechanged as follows: the source IP address may be changed from Phone 1Private to Phone 1 Public, the source port may remain UNCHANGED, thedestination IP address may be set to Phone 2 Public, and the destinationport may be set to Phone 2, as indicated.

In step 1026 the SG 170 may perform IPSec encryption on the call data(packet). The original packet is encapsulated in a new packet with asource address of the external interface address of the Service Gateway,and the destination address on the VPN Concentrator. In 1030, the SG 170may forward the data over the selected tunnel. In step 1032, the datamay traverse the customer network, and may reach a VPN Concentrator136A, as shown in step 1034. In step 1036, the VPN Concentrator 136A maydecrypt the call data.

In step 1038, the VPN Concentrator 136A may determine if the destinationroute is local or on a tunnel. It should be noted that, depending uponwhether the destination route used a local gateway or a tunnel, a secondVPN Concentrator 136B or the first VPN Concentrator 136A, respectively,performs the steps 1046 and 1048, below, as shown.

If the destination route uses a local gateway, then in step 1040, theVPN Concentrator 136A may route the call data to a local router, whichmay forward the data to a second VPN Concentrator 136B, as indicated instep 1042. In step 1044 the data may reach the second VPN Concentrator136B, which may select a destination tunnel based on the destination IPaddress, as indicated in step 1046. In step 1048, the second VPNConcentrator 136B may perform IPSec encryption on the data.

Referring back to step 1038, if the destination route is on a tunnel,then in step 1046, the VPN Concentrator 136A may select a destinationtunnel based on the destination IP address, as indicated in step 1046.In step 1048, the VPN Concentrator 136A may perform IPSec encryption onthe data.

In step 1050, the data may be forwarded over the selected tunnel. Then,in step 1058 the data may traverse the channel partner network, and instep 1060 may reach the second SG 170B. The second SG 170B may decryptthe data, as indicated in step 1062, perform NAPPT in step 1064. In oneembodiment, the packet header may now include a source IP address, setto Phone 1 Public NAT, a source port which remains the UNCHANGED Phone 1port, a destination IP address, changed from Phone 2 Public to Phone 2Private, and a destination port which remains as the UNCHANGED Phone 2port.

Then, the second SG 170B may forward the data out through the localinterface, as shown in step 1066.

In step 1068, the system may determine if the IP telephone 120A receivesthe data, i.e., responds to ARP. If the IP telephone 120A does notreceive the data, then the packet may be dropped, as indicated in step1022, the session may fail and the process may terminate. If the IPtelephone 120A does receive the data, then in step 1070 the second IPtelephone 120B may process the RTP data.

In step 1072, the system may determine if IP telephone 120B responds,i.e., receives the data. If IP telephone 120B does not respond, then thesession may fail, as indicated in step 1006, and the process mayterminate. If IP telephone 120B responds, then in step 1074 the systemmay determine if the RTP session succeeds.

If the RTP session succeeded, then in step 1076, the RTP exchange maycontinue until data exchange is complete, and the process may terminate.

FIG. 11: A Solution to the Triangle Problem

FIG. 11 illustrates one embodiment of a solution to the triangleproblem, described above, which may be implemented by variousembodiments of the present invention. It is noted that FIG. 11illustrates one exemplary embodiment of the triangle problem solutionprocess, and that this solution process may be performed in variousmanners according to the present invention. It is further noted thatvarious of the steps shown may be performed in different orders oromitted, or various additional steps may be performed as desired.

As FIG. 11 shows, in 1102, a Call Setup request may be received. In oneembodiment, the Call Setup request may include a source IP address and adestination telephone number.

In 1104, a first Media Gateway may be selected based on the source IPaddress. For example, in one embodiment, the first Media Gateway may beselected via a table look-up, where an association may be stored betweensource IP addresses and corresponding Media Gateways.

In 1106, a second Media Gateway may be selected based on the destinationtelephone number. In one embodiment, the second Media Gateway may alsobe selected via a table look-up, where an association may be storedbetween destination telephone numbers and corresponding Media Gateways.

It should be noted that in various embodiments, the first and/or secondMedia Gateways may be IP telephones, Trunking Gateways, Fax machines,pagers, or any other type of Media Gateway. In an embodiment where oneof the Media Gateways is a Trunking Gateway, the Trunking Gateway mayprovide an interface to the Public Switched Telephone Network (PSTN),whereby communications with external telephony devices may be performed.

In 1108, a public IP address of the first Media Gateway may be comparedto a public IP address of the second Media Gateway, and if the public IPaddress of the first Media Gateway is the same as the public IP addressof the second Media Gateway, then in 1110, a private IP address of thefirst Media Gateway and a private IP address of the second Media Gatewaymay be selected for Call Setup.

If the public IP address of the first Media Gateway is not the same asthe public IP address of the second Media Gateway, then in 1112 thepublic IP address of the first Media Gateway and the public IP addressof the second Media Gateway may be selected for Call Setup.

In 1114, the selected IP address (whether private or public) of thefirst Media Gateway may be sent to the second Media Gateway, and theselected IP address of the second Media Gateway may be sent to the firstMedia Gateway, according to one embodiment. Thus, the Media Gateways maybe provided with respective destination IP addresses for the currentcall session. In one embodiment, these IP addresses may be provided by aregistration process prior to the Call Setup request, as described abovewith reference to FIGS. 4A, 4B, 6A, 6B and 6C. For example, in oneembodiment, a Media Gateway may register with Media Gateway Controller150, by sending the Media Gateway's public IP address. The public IPaddress may be received and stored (e.g., by the Media GatewayController 150) for later reference in the Call Setup process. In thecase where the Media Gateway is internal to the system (as opposed to aTrunking Gateway leading to external IP devices), registering the MediaGateway (e.g., with the Media Gateway Controller 150) may also includesending a private IP address of the Media Gateway, and storing theprivate IP address for use as described above.

Finally, in 1116, the first Media Gateway may send data to the secondMedia Gateway using the selected IP address of the second Media Gateway,and the second Media Gateway may send data to the first Media Gatewayusing the selected IP address of the first Media Gateway. In otherwords, the call session between the two Media Gateways may proceed.

Thus, by receiving and storing distinguishing information related to theMedia Gateways, such as IP addresses and associated telephone numbers,among others, the method may distinguish between bilateral internal callsessions and call sessions involving an internal IP telephone and anexternal device, e.g., an external telephone interfacing through aTrunking Gateway to an internal IP telephone.

FIGS. 2-11 illustrate various exemplary applications where the inventionmay be used. However, it is noted that the invention is not limited tothese applications, but rather may be used in any of variousapplications.

Memory and Carrier Medium

The system preferably includes a memory medium on which softwareaccording to an embodiment of the present invention may be stored. Theterm “memory medium” is intended to include an installation medium,e.g., a CD-ROM, floppy disks, or tape device; a computer system memoryor random access memory (RAM) such as DRAM, SRAM, EDO RAM, RRAM, etc.;or a non-volatile memory such as a magnetic media, e.g., a hard drive,or optical storage. The memory medium may include other types of memoryas well, or combinations thereof.

In addition, the memory medium may be located in a first computer inwhich the software program is stored or executed, or may be located in asecond different computer which connects to the first computer over anetwork, such as the Internet. In the latter instance, the secondcomputer provides the program instructions to the first computer forexecution. Also, the computer system may take various forms, including apersonal computer system, mainframe computer system, workstation,network appliance, Internet appliance, personal digital assistant (PDA),television set-top box, or other device. In general, the term “computersystem” can be broadly defined to encompass any device having at leastone processor which executes instructions from a memory medium, or anydevice which includes programmable logic that is configurable to performa method or algorithm.

Various embodiments further include receiving or storing instructionsand/or data implemented in accordance with the foregoing descriptionupon a carrier medium. Suitable carrier media include a memory medium asdescribed above, as well as signals such as electrical, electromagnetic,or digital signals, conveyed via a communication medium such as networksand/or a wireless link.

Although the embodiments above have been described in considerabledetail, numerous variations and modifications will become apparent tothose skilled in the art once the above disclosure is fully appreciated.It is intended that the following claims be interpreted to embrace allsuch variations and modifications.

1. A method for configuring an IP telephone, comprising: receiving anidentifier from the IP telephone; determining if a MAC ID for the IPtelephone is valid; if the MAC ID is determined to be valid, determiningif the identifier is valid; if the identifier is valid, assigning arange of port numbers to the IP telephone based on the identifier,wherein the IP telephone is operable to use at least a subset of therange of port numbers to send or receive IP communications.
 2. Themethod of claim 1, wherein said range of port numbers comprises portswhich are not reserved for use by other IP protocols.
 3. The method ofclaim 1, further comprising: mediating IP communications between the IPtelephone and an IP device, wherein the IP telephone uses at least asubset of the range of port numbers to send or receive said IPcommunications.
 4. The method of claim 3, wherein said mediating the IPcommunications comprises: receiving a data packet from the IP telephone,performing a network address persistent port translation (NAPPT) on thedata packet; and sending the data packet to the IP device.
 5. The methodof claim 4, wherein the data packet comprises a private source IPaddress, a source port number, and destination information associatedwith the IP device, wherein the private source IP address comprises aprivate IP address of the IP telephone, and wherein the source portnumber comprises a port number in the assigned range of port numbers;and wherein said performing a network address persistent porttranslation (NAPPT) on the data packet comprises changing the privatesource IP address to a public source IP address while leaving the sourceport number unchanged, and wherein the public source IP address and thesource port number may be used to uniquely identify the IP telephone. 6.The method of claim 3, wherein said mediating the IP communicationscomprises: receiving a data packet from the IP device; performing anetwork address persistent port translation (NAPPT) on the data packet;and sending the data packet to the IP telephone.
 7. The method of claim6, wherein the data packet comprises a public destination IP address, adestination port number; and source information associated with the IPdevice, wherein the destination port number comprises a port number inthe assigned range of port numbers, and wherein the public destinationIP address and the destination port number may be used to uniquelyidentify the IP telephone; and wherein said performing a network addresspersistent port translation (NAPPT) on the data packet comprises usingthe public destination IP address and the destination port number touniquely identify the IP telephone, and changing the public destinationIP address to a private destination IP address while leaving thedestination port number unchanged, wherein the private IP addresscomprises an IP address of the IP telephone.
 8. The method of claim 1,wherein the identifier comprises a vendor class identifier.
 9. Themethod of claim 1, wherein said identifier is comprised in a DHCPdiscover message, the method further comprising: issuing a DHCP offer tothe IP telephone if the identifier is determined to be valid, whereinthe DHCP offer comprises DHCP lease information based on the validatedidentifier; the IP telephone issuing a DHCP request in response to theissued DHCP offer; storing the DHCP lease information in response to theissued DHCP request; the IP telephone storing the DHCP leaseinformation; and the IP telephone enabling DHCP settings comprised inthe DHCP lease information.
 10. The method of claim 9, wherein said DHCPlease information includes the range of port numbers and informationindicating operational software for the IP telephone, the method furthercomprising: the IP telephone executing the indicated operationalsoftware to enable said IP communications.
 11. The method of claim 9,wherein said DHCP lease information includes the range of port numbersand information indicating operational software for the IP telephone,the method further comprising: the IP telephone issuing a request forthe operational software; providing the operational software to the IPtelephone in response to the issued request; and the IP telephoneexecuting the provided operational software to enable said IPcommunications.
 12. The method of claim 11, wherein said issuing therequest for the operational software comprises issuing a read request toa file transfer server, wherein said file transfer server performs saidproviding the operational software to the IP telephone.
 13. The methodof claim 12, wherein the file transfer server comprises a TFTP (TrivialFile Transfer Protocol) server.
 14. The method of claim 1, wherein therange of port numbers comprises one or more port numbers.
 15. A systemfor performing IP telephony, comprising: a network; an IP telephone; aService Gateway, wherein the Service Gateway is operable to couple tothe IP telephone through the network; wherein the IP telephone isoperable to send an identifier to the Service Gateway; wherein theService Gateway is operable to: receive an identifier from the IPtelephone; determine if a MAC ID for the IP telephone is valid; if theMAC ID is determined to be valid, determine if the identifier is valid;and if the identifier is valid, assign a range of port numbers to the IPtelephone based on the identifier; wherein the IP telephone is operableto use at least a subset of the range of port numbers to send or receiveIP communications.
 16. The system of claim 15, wherein said range ofport numbers comprises ports which are not reserved for use by other IPprotocols.
 17. The system of claim 15, wherein the Service Gateway isfurther operable to mediate IP communications between the IP telephoneand an IP device.
 18. The system of claim 17, wherein, in mediating theIP communications the Service Gateway is operable to: receive a datapacket from the IP telephone, perform a network address persistent porttranslation (NAPPT) on the data packet; and send the data packet to theIP device.
 19. The system of claim 18, wherein the data packet comprisesa private source IP address, a source port number, and destinationinformation associated with the IP device, wherein the private source IPaddress comprises a private IP address of the IP telephone, and whereinthe source port number comprises a port number in the assigned range ofport numbers; and wherein said performing a network address persistentport translation (NAPPT) on the data packet comprises changing theprivate source IP address to a public source IP address while leavingthe source port number unchanged, and wherein the public source IPaddress and the source port number may be used to uniquely identify theIP telephone.
 20. The system of claim 17, wherein, in mediating the IPcommunications the Service Gateway is operable to: receive a data packetfrom the IP device; perform a network address persistent porttranslation (NAPPT) on the data packet; and send the data packet to theIP telephone.
 21. The system of claim 20, wherein the data packetcomprises a public destination IP address, a destination port number;and source information associated with the IP device, wherein thedestination port number comprises a port number in the assigned range ofport numbers, and wherein the public destination IP address and thedestination port number may be used to uniquely identify the IPtelephone; and wherein said performing a network address persistent porttranslation (NAPPT) on the data packet comprises using the publicdestination IP address and the destination port number to uniquelyidentify the IP telephone, and changing the public destination IPaddress to a private destination IP address while leaving thedestination port number unchanged, wherein the private IP addresscomprises an IP address of the IP telephone.
 22. The system of claim 15,wherein the identifier comprises a vendor class identifier.
 23. Thesystem of claim 15, wherein said identifier is comprised in a DHCPdiscover message, wherein the Service Gateway is further operable to:issue a DHCP offer to the IP telephone if the identifier is determinedto be valid, wherein the DHCP offer comprises DHCP lease informationbased on the validated identifier; wherein the IP telephone is furtheroperable to: issue a DHCP request in response to the issued DHCP offer;store the DHCP lease information; and enable DHCP settings comprised inthe DHCP lease information; and wherein the Service Gateway is furtheroperable to: store the DHCP lease information in response to the issuedDHCP request.
 24. The system of claim 23, wherein said DHCP leaseinformation includes the range of port numbers and informationindicating operational software for the IP telephone, wherein the IPtelephone is further operable to: execute the indicated operationalsoftware to enable said IP communications.
 25. The system of claim 23,wherein said DHCP lease information includes the range of port numbersand information indicating operational software for the IP telephone,wherein the IP telephone is further operable to: issue a request for theoperational software; wherein the Service Gateway is further operableto: provide the operational software to the IP telephone in response tothe issued request; and wherein the IP telephone is further operable to:execute the provided operational software to enable said IPcommunications.
 26. The system of claim 25, wherein, in issuing therequest for the operational software, the IP telephone is operable toissue a read request to a file transfer server, wherein said filetransfer server is operable to provide the operational software to theIP telephone.
 27. The system of claim 26, wherein the file transferserver comprises a TFTP (Trivial File Transfer Protocol) server.
 28. Thesystem of claim 15, wherein the range of port numbers comprises one ormore port numbers.
 29. A memory medium, wherein the memory medium storesprogram instructions which are executable to perform: receiving anidentifier from the IP telephone; determining if a MAC ID for the IPtelephone is valid; if the MAC ID is determined to be valid, determiningif the identifier is valid; and if the identifier is valid, assigning arange of port numbers to the IP telephone based on the identifier,wherein the IP telephone is operable to use at least a subset of therange of port numbers to send or receive IP communications.
 30. Thememory medium of claim 29, wherein said range of port numbers comprisesports which are not reserved for use by other IP protocols.
 31. Thememory medium of claim 29, wherein the program instructions are furtherexecutable to perform: mediating IP communications between the IPtelephone and an IP device, wherein the IP telephone uses at least asubset of the range of port numbers to send or receive said IPcommunications.
 32. The memory medium of claim 31, wherein saidmediating the IP communications comprises: receiving a data packet fromthe IP telephone, performing a network address persistent porttranslation (NAPPT) on the data packet; and sending the data packet tothe IP device.
 33. The memory medium of claim 32, wherein the datapacket comprises a private source IP address, a source port number, anddestination information associated with the IP device, wherein theprivate source IP address comprises a private IP address of the IPtelephone, and wherein the source port number comprises a port number inthe assigned range of port numbers; and wherein said performing anetwork address persistent port translation (NAPPT) on the data packetcomprises changing the private source IP address to a public source IPaddress while leaving the source port number unchanged, and wherein thepublic source IP address and the source port number may be used touniquely identify the IP telephone.
 34. The memory medium of claim 31,wherein said mediating the IP communications comprises: receiving a datapacket from the IP device; performing a network address persistent porttranslation (NAPPT) on the data packet; and sending the data packet tothe IP telephone.
 35. The memory medium of claim 34, wherein the datapacket comprises a public destination IP address, a destination portnumber; and source information associated with the IP device, whereinthe destination port number comprises a port number in the assignedrange of port numbers, and wherein the public destination IP address andthe destination port number may be used to uniquely identify the IPtelephone; and wherein said performing a network address persistent porttranslation (NAPPT) on the data packet comprises using the publicdestination IP address and the destination port number to uniquelyidentify the IP telephone, and changing the public destination IPaddress to a private destination IP address while leaving thedestination port number unchanged, wherein the private IP addresscomprises an IP address of the IP telephone.
 36. The memory medium ofclaim 29, wherein the identifier comprises a vendor class identifier.37. The memory medium of claim 29, wherein said identifier is comprisedin a DHCP discover message, wherein the program instructions are furtherexecutable to perform: issuing a DHCP offer to the IP telephone if theidentifier is determined to be valid, wherein the DHCP offer comprisesDHCP lease information based on the validated identifier; receiving aDHCP request from the IP telephone in response to the issued DHCP offer;and storing the DHCP lease information in response to the issued DHCPrequest; wherein said program instructions comprise IP telephone programinstructions which are executable to: store the DHCP lease information;and enable DHCP settings comprised in the DHCP lease information. 38.The memory medium of claim 37, wherein said DHCP lease informationincludes the range of port numbers and information indicatingoperational software for the IP telephone, wherein the indicatedoperational software is executable by the IP telephone to enable said IPcommunications.
 39. The memory medium of claim 37, wherein said DHCPlease information includes the range of port numbers and informationindicating operational software for the IP telephone, wherein theprogram instructions are further executable to perform: receiving arequest for the operational software from the IP telephone; providingthe operational software to the IP telephone in response to the issuedrequest; and wherein the provided operational software is executable bythe IP telephone to enable said IP communications.
 40. The memory mediumof claim 39, wherein the IP telephone program instructions areexecutable to issue a read request to a file transfer server; whereinsaid program instructions further comprise file transfer server programinstructions executable to perform said providing the operationalsoftware to the IP telephone.
 41. The memory medium of claim 40, whereinthe file transfer server comprises a TFTP (Trivial File TransferProtocol) server.
 42. The memory medium of claim 29, wherein the rangeof port numbers comprises one or more port numbers.
 43. A servicegateway for use in an IP telephony network, wherein the service gatewayis configured to: couple one or more IP telephones to the network;receive an identifier from an IP telephone; determine if a MAC ID forthe IP telephone is valid; if the MAC ID is determined to be valid,determine if the identifier is valid; and if the identifier is valid,assign a range of port numbers to the IP telephone based on theidentifier; wherein at least a subset of the range of port numbers areusable by the IP telephone to send or receive IP communications.
 44. Theservice gateway of claim 43, wherein said range of port numberscomprises ports which are not reserved for use by other IP protocols.45. The service gateway of claim 43, wherein the service gateway isfurther configured to mediate IP communications between the IP telephoneand an IP device.
 46. The service gateway of claim 45, wherein, inmediating the IP communications the service gateway is furtherconfigured to: receive a data packet from the IP telephone, perform anetwork address persistent port translation (NAPPT) on the data packet;and send the data packet to the IP device.
 47. The service gateway ofclaim 46, wherein the data packet comprises a private source IP address,a source port number, and destination information associated with the IPdevice, wherein the private source IP address comprises a private IPaddress of the IP telephone, and wherein the source port numbercomprises a port number in the assigned range of port numbers; andwherein said performing a network address persistent port translation(NAPPT) on the data packet comprises changing the private source IPaddress to a public source IP address while leaving the source portnumber unchanged, and wherein the public source IP address and thesource port number may be used to uniquely identify the IP telephone.48. The service gateway of claim 45, wherein, in mediating the IPcommunications, the service gateway is further configured to: receive adata packet from the IP device; perform a network address persistentport translation (NAPPT) on the data packet; and send the data packet tothe IP telephone.
 49. The service gateway of claim 48, wherein the datapacket comprises a public destination IP address, a destination portnumber; and source information associated with the IP device, whereinthe destination port number comprises a port number in the assignedrange of port numbers, and wherein the public destination IP address andthe destination port number may be used to uniquely identify the IPtelephone; and wherein said performing a network address persistent porttranslation (NAPPT) on the data packet comprises using the publicdestination IP address and the destination port number to uniquelyidentify the IP telephone, and changing the public destination IPaddress to a private destination IP address while leaving thedestination port number unchanged, wherein the private IP addresscomprises an IP address of the IP telephone.
 50. The service gateway ofclaim 43, wherein the identifier comprises a vendor class identifier.51. The service gateway of claim 43, wherein said identifier iscomprised in a DHCP discover message, wherein the service gateway isfurther configured to: issue a DHCP offer to the IP telephone if theidentifier is determined to be valid, wherein the DHCP offer comprisesDHCP lease information based on the validated identifier; wherein the IPtelephone is further operable to: issue a DHCP request in response tothe issued DHCP offer; store the DHCP lease information; and enable DHCPsettings comprised in the DHCP lease information; and wherein theservice gateway is further configured to: store the DHCP leaseinformation in response to the issued DHCP request.
 52. The servicegateway of claim 51, wherein said DHCP lease information includes therange of port numbers and information indicating operational softwarefor the IP telephone, wherein the IP telephone is further operable to:execute the indicated operational software to enable said IPcommunications.
 53. The service gateway of claim 51, wherein said DHCPlease information includes the range of port numbers and informationindicating operational software for the IP telephone, wherein the IPtelephone is further operable to issue a request for the operationalsoftware; wherein the service gateway is further operable to provide theoperational software to the IP telephone in response to the issuedrequest; and wherein the IP telephone is further operable to execute theprovided operational software to enable said IP communications.
 54. Theservice gateway of claim 53, wherein, in issuing the request for theoperational software, the IP telephone is operable to issue a readrequest to a file transfer server, wherein said file transfer server isoperable to provide the operational software to the IP telephone. 55.The service gateway of claim 54, wherein the file transfer servercomprises a TFTP (Trivial File Transfer Protocol) server.
 56. Theservice gateway of claim 43, wherein the range of port numbers comprisesone or more port numbers.